招标人自中标通知书发出（）日内，应和中标人签订物业服务合同。
A.10
B.15
C.30
D.60
参考答案：C
---Teenagers are sometimes made _________ ______ they are not_________．
--- I agree．
A．to do, what, interested in
B．to do, that, interested
C．do, that, interested in
D．do, what, interested
（）检测器不适合测定丙酮
A.MSD
B.FID
C.PID
D.ECD
